Generally, a transmission line for transmitting a high frequency signal is provided in wireless devices such as a smartphone and a tablet personal computer (PC).
Conventionally, a coaxial cable has been mainly used as the transmission line. However, recently, due to a miniaturization trend of wireless devices, an interior space of the wireless devices has gradually become narrower. Thus, a flexible circuit board occupying a smaller space compared to the coaxial cable has been used.
In addition to the miniaturization trend of wireless devices, various functions are added to wireless devices, and an interior space of the wireless devices becomes further narrower. In response to such a trend, there is a need to develop a more miniaturized flexible circuit board.